The invention relates generally to copying.
More particularly, the invention relates to the copying of photographic originals, e.g. negatives.
It is known to splice or otherwise join a series of individual, exposed and developed film strips end-to-end prior to copying the exposures or originals on the film strips. The resulting band of coherent film strips is convoluted into a roll which is then inserted in a copying apparatus designed to advance the originals from the roll to a copying station. The originals are rewound into a roll after copying.
The apparatus may have a measuring station upstream of the copying station for measuring the densities of the originals in the three primary colors. The measuring station is connected with an exposure control device which constitutes part of the copying station and controls the exposures of the originals as a function of the density values. A magazine or storage device having a variable capacity may be disposed between the measuring station and the copying station to permit accumulation of the originals. This may be desirable if there is to be a lapse between density measurement of the originals and copying of the latter.
The German patent No. 19 14 360 discloses a copying apparatus of this type. This apparatus is designed in such a manner that the density values for all of the originals of a film strip are measured and evaluated prior to copying any of the originals of the film strip. Since the density values for the entire film strip are then available before any copying is performed on the film strip, a more accurate determination may be made of the amounts of light required during exposure. A magazine is disposed between the measuring and copying stations of the apparatus of the German patent, and the maximum storage capacity of the magazine is precisely sufficient for the longest film strip to be processed during normal operation. The magazine is provided with a pair of displaceable rollers which enable the storage capacity of the magazine to be changed when the length of the film strips to be processed changes.
The magazine of the German patent is designed on the assumption that all of the film strips in a band of coherent strips have the same length. If the length of the film strips is changed, the storage capacity of the magazine must be adjusted.
In order to carry out a copying operation in a practical fashion, it is necessary to have the ability to combine film strips of different length into a single band. For instance, strips of 135 type film come with 36 exposures of 24.times.36 mm each; 24 exposures of 24.times.36 mm each; and 12 exposures of 24.times.36 mm each. The various strips may be mixed when they come in for processing, and strips with different numbers of exposures may have to be combined in a single band. Furthermore, in worse cases, it may be necessary to incorporate sections of torn film strips into a band. Such sections may be even shorter than the shortest intact film strip in the band.
When a band contains film strips having different lengths, more than one splice or junction may be located between the density measuring station and the copying station, i.e. more than one splice or junction may be located in the region of the magazine. In such an event, portions of several different film strips are disposed between the density measuring station and the copying station. This leads to synchronization problems. Thus, there exists the possibility that density values derived from one film strip become associated with another film strip and are used for exposure control of the latter rather than for exposure control of the film strip from which the density values were actually obtained.